Checking the class_exists for Wikibase which would complicate enabling preload (feature of php 7.4) can be found everywhere in Wikibase-related extensions: [[https://codesearch.wmcloud.org/extensions/?q=class_exists&i=nope&files=&excludeFiles=&repos=|the whole list]]. For example: [[https://gerrit.wikimedia.org/g/mediawiki/extensions/WikidataPageBanner/+/7666284c3e9dad695f550ad15e04bc821fe39478/includes/WikidataPageBannerFunctions.php#303| In WikidataPageBanner]]. They are there because Wikibase wasn't being loaded using extension registry (but that got fixed recently) and now they can simply migrated to `ExtensionRegistry::isLoaded('WikibaseClient')` and `ExtensionRegistry::isLoaded('WikibaseRepo')`.
List of related ones:
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/MobileFrontend/+/423807c4261f2e00e75fbe0b4d24363a90d4016e/includes/ExtMobileFrontend.php#207|MobileFrontend]]
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Echo/+/1d6a2bc5c749308c2fe37715819575480052be37/maintenance/generateSampleNotifications.php#539|Echo]]
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Math/+/6e52bc280717ea2337bc41750df7103d16c952df/src/MathHooks.php#401|Math]] (twice)
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Citoid/+/1d1d1209ce16c42bb5829243fa2263d4dc504bd4/includes/CitoidHooks.php#47|Citoid]]
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/WikibaseMediaInfo/+/0cc7c405b63827706c2ea37cbfc54e74ae1f0ff9/src/WikibaseMediaInfoHooks.php#137|Wikibase MediaInfo]]
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Wikidata.org/+/4a6e9b584d1d5db5a0617a29fbd12b17fa6ec19f/src/Hooks.php#33|Wikidata.org]]
[] [[https://gerrit.wikimedia.org/g/mediawiki/extensions/WikidataPageBanner/+/7666284c3e9dad695f550ad15e04bc821fe39478/includes/WikidataPageBannerFunctions.php|WikidataPageBanner]]